Contribution à l’étude de l’enthalpie du verre
de silice densifie

Couty, R.; Sabatier, Germain

doi:10.1051/jcp/1978750843

Cited by 10 publications

(5 citation statements)

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“…The origin of this behavior can be traced to changing Si-Si short-range order with pressure. The real-space Si-Si pair-correlation function reveals that the average nearest-neighbor distance between Si atoms decreases with pressure, in agreement with previous calculations [9,18,29], while the corresponding first peak in the Si-Si pair-correlation function reduces in magnitude and broadens significantly into a structure with almost double-peak character. From this analysis, however, we still cannot extract a clear correlation between the changes in the structure factor and the EOS.…”

supporting

confidence: 90%

“…The increase in density was attributed to the rotation of the silica tetrahedra. X-ray [18] and neutron [9] diffraction, infrared and Raman spectroscopy revealed a decrease in the average Si-O-Si angle and a small increase in the Si-O bond distance [13]. Moreover, x-ray diffraction measurements [17] have shown that the characteristic first sharp diffraction peak (FSDP) associated with the medium-range order (MRO) of these materials is significantly reduced upon densification.…”

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confidence: 99%

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Transformations in the Medium-Range Order of Fused Silica under High Pressure

et al. 2003

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Molecular dynamics simulations of fused silica at shock pressures reproduce the experimental equation of state of this material and explain its characteristic shape. We demonstrate that shock waves modify the medium-range order of this amorphous system, producing changes that are only clearly revealed by its ring size distribution. The ring size distribution remains practically unchanged during elastic compression but varies continuously after the transition to the plastic regime.

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confidence: 90%

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confidence: 99%

Transformations in the Medium-Range Order of Fused Silica under High Pressure

et al. 2003

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“…An additional parameter like the fictive pressure, i.e., the pressure at which configurational changes have been blocked, is thus insufficient and a whole fictive stress tensor should be specified instead. Indeed, Couty & Sabatier (1968) reported that the enthalpy of densified SiO 2 glass depends not only on the density of the sample, but also on the stress conditions of the densification experiments. On the average, the enthalpy difference between samples with densities of 2.64 and 2.2 g/cm 3 amounts to the very large value of 18 kJ/mol, which is similar to the work done on the samples to get them densified (Couty & Sabatier, 1968).…”

Section: Thermodynamics Of Glassesmentioning

confidence: 99%

“…In this two-step process, the total enthalpy of 44 kJ/mol thus in cludes a significant enthalpy of transformation from a densified to "normal" SiO 2 glass {cf. Couty & Sabatier, 1968). Hence, amorphization can be a rather complex process, even for a structurally simple mineral heated at atmospheric pressure.…”

Section: A Few Examplesmentioning

confidence: 99%

Pressure-induced amorphization of minerals: a review

Richet

Gillet

1997

ejm

169

126

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A variety of minerals transform to an amorphous material when statically compressed to a few tens of GPa. With quartz and the quartz-type forms of GeO 2 and A1PO 4 as examples, pressure-induced amorphization is first described with reference to differential stresses, crystalline transformations, compression mechanisms and shearing processes. Less comprehensive information is available for the amorphization of other minerals, but similar features are nevertheless observed for framework silicates, pyroxenes, olivines and hydrous silicates. The differences and similarities between amorphous substances obtained by cooling of liquids, static compression or decompression of crystals, moderate heating of high-pressure minerals at 1 atm, and shock waves are then reviewed. Finally, the thermodynamics of amorphization is discussed and the mechanistic interpretations of amorphization are presented, with special reference to elastic and dynamic instabilities and shearing processes.

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“…There have also been many experiments utilizing a wide range of experimental techniques to probe the change in the Si−O−Si bridging angle in densified amorphous silica. The reduction in the average Si−O−Si angle after a densification between 16% and 25% is found to be around 5°. − However, these measurements on the densified silica were taken after the pressure was released, a situation unlike our current experiment. Theoretical studies of in-situ densification show larger changes with a decrease from 147.4° for normal density to 133.7° for a 20% densified sample under pressure .…”

Section: Discussionmentioning

confidence: 60%

Elasticity through Nanoscale Distortions in Periodic Surfactant-Templated Porous Silica under High Pressure

Zhao

Chronister

et al. 2002

J. Phys. Chem. B

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High-pressure infrared absorption spectroscopy is used to examine changes in local bonding upon hydrostatic compression in both ordered surfactant-templated mesoporous silica and sintered sol−gel silica with a goal of connecting atomic scale structural changes with variations in nanoscale periodicity. High-pressure IR absorption spectra are analyzed on the basis of a noncentral force model. It is found that the intertetrahedral bond angle and its distribution width in both the dense and the mesoporous silica decrease at elevated pressure up to 4 GPa. With increasing pressure above this value, decreases in the average bond angle and distribution width cease in the mesoporous silica, while they continue in the bulk material. The results suggest that in the mesoporous silica the nanometer length scale of the silica framework makes it energetically unfavorable to form high-density atomic scale structures at higher pressures (>4 GPa). Instead, further compression of the mesoporous silica takes place by distortion of the periodic pore structures on the nanometer scale (deformation of pores). Surprisingly, upon the release of pressure, structural changes on both the nanometer and atomic length scales are reversible. The results suggest that reversible nanometer scale distortions in periodic porous materials can replace the irreversible atomic scale distortions observed in bulk amorphous silica.

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Contribution à l’étude de l’enthalpie du verre de silice densifie

Cited by 10 publications

References 0 publications

Transformations in the Medium-Range Order of Fused Silica under High Pressure

Transformations in the Medium-Range Order of Fused Silica under High Pressure

Pressure-induced amorphization of minerals: a review

Elasticity through Nanoscale Distortions in Periodic Surfactant-Templated Porous Silica under High Pressure

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